Axiom Home Page Forums General Discussion Home Theater Logic 7 and surrounds: presence up-front to back?

Hi:

Does the surround sound from Logic 7 (5.1 music mode) when playing an ordinary cd (analog connnection) change in presence time to time-i.e., Elton John's voice (could be instruments also) from Crocodile Rock seems in the background (sound from speaker) and then all of a sudden the vocal appears upfront and then maybe repeats the pattern once in the while ?

Should the presence from the surrounds using Logic 7 or Pro Logic II stay constant?

If the vocal is up front it should remain that way through the song.

(I have been noticing volume changes (louder softer) and found out that the presence from the surrounds are causing it-music from surrounds going from upfront in presentation to back (bookshelfs are used as surrounds).

Any help would be most welcomed,


Intune

The goal of Logic 7 and PLII is to produce consistent, natural surround from stereo sources. They do pretty good. If anything I think PLII is too conservative. On some material there's pretty good surround and on others, very little. Dolby has a document on their web site with stereo material that PLII works well on.

However there may be a few situations where PLII or L7 do something artificial sounding, such as making main vocals temporarily come out of the surrounds, or ping-ponging a vocal or instrument speaker to speaker. In my experience that's extremely rare with PLII. Don't know about L7.

It's funny you mentioned Crocodile Rock. I just got the remastered stereo CD of Elton John - Don't Shoot Me, and the audio quality wasn't that good. It was somewhat flat and PLII produced relatively little surround. Likewise for the earlier albums.

By contrast the audio quality of the stereo CD Goodbye Yellow Brick Road was superb, and the SACD version of that is mind-blowing. The same producer Gus Dudgeon did both albums, and they were both done in the same recording studio. I don't understand why the huge difference.

If you have an SACD player, I strongly suggest getting the SACD of Goodbye Yellow Brick Road. IMO it's nearly good as Pink Floyd -- Dark Side of The Moon from an audio engineering standpoint. If you don't SACD, the stereo CD is vastly better from an audio and mixing standpoint than the Don't Shoot Me and earlier albums. Why the huge difference is a mystery.

My understanding is quite general. But I think both Dolby PLII and Harman Kardon Logic 7 work best with acoustically recorded sound, such as a classical or live jazz performance, where each stereo channel contains some "information" about the other because each main steeo microphone picks up delayed or echoed sound that the other main microphone records more directly. The two channels are then processed to isolate these "live" artifacts from the more directly recorded music, then the whole thing is remixed on the fly into multiple surround channels as appropriate.

Much popular music -- I'll bet your Elton John recording is like this -- is created as much as in the engeineer's booth as in the live studio. In other words, which sounds are on which stereo channel is very much a function of what the recording engineer considered good stereo, and how he mixed multiple microphone channels into two on the final recording. That may bear little relation to what the live acoustic mix was like inside the studio.

So unlike a concert-like performance -- which likely is recreated more accurately with PLII or Logic 7 -- the artificially pop-mixed stereo may not play any better and may even sound worse.

So the source material needs to contain some information for logic 7 or PLII to sound properly like live jazz performances? Then how many regular Pop/blues/Rock Cds can sound good with 7 or PLII (better)?

So, far very few CDs of mine do. Take My Generation SACD (2CH-analog), if I listen to My Generation (song) L7, part way through my right surround goes very high in volume and then it will go back to it's normal sound seconds later. If I listen to The Beatles "For Sale" CD, I get barely any surround sound. When I listen to the Grass Roots anthology I get vocals and instrumentals that drift in and out but not completely from the surrounds. The overall result is fluctuations in volume and presentation that become annoying very quickly.

So, I'm thinking for a 99.9% music listener is surround processing really worth the cost for a mainstream music listener.

(Note: I do realize my sound problems could be a receiver malfunction-speakers,cables, and player seem to be operating fine.)

In reply to:

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The overall result is fluctuations in volume and presentation that become annoying very quickly.

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It is interesting that this was noted recently. We had a discussion on DPL2 awhile back and i used the incorrect term of 'faked' to describe the DPL2. Ultimately it is an algorithm extracting ambient information from the data stream and presenting it to the surround channels. Alan referred to it as a 'reconstruction' of original surround signal info. It is not faked per se although sometimes i do find its presentation sounds that way. I once did a test of my surround channels for something unrelated and i had all my speakers unplugged except for the surrounds. The sounds coming from them certainly wavered in and out with volumes and voices such that i could not tell what song was even playing unless i plugged one of my main speakers back in. It certainly was a head scratcher as to what the heck the DPL2 was doing.
Although i believe that DPL2 is pretty good, it does not hold a candle to dvd-a/sacd with all channels running.
THAT sound is just stellar.

IT, as boomer briefly touched on, DPLII and Logic 7 work with information that's already part of the two stereo channels; they don't create any new sounds, such as the echoes some DSP does. In stereo the mikes pick up both direct sounds from the performers and indirect reflected out of phase sound from the side and back walls. A simplified version of what's going on is that if the DPLII or Logic 7 reads direct sound stronger in the left stereo channel it sends most of that to the left front speaker. Direct sound stronger in the right channel conversely gets sent mainly to the right speaker. Direct sound about equally strong in both channels gets sent mainly to the center speaker. Sound which it reads as reflected out of phase on the left channel gets sent mainly to the left surround speaker and conversely for the right surround speaker.

Since the majority of sound reaching someone at the performance(unless they're in the conductor's lap)is actually reflected from the side and back walls, it's less natural for all that sound to be coming from two speakers in front of you, as compared to some of the reflected sound coming from side or back speakers(contrary to those who complain that stereo recordings don't sound natural on a surround system).

My view is that this works rather well on the classical recordings which I listen to, depending on how much out of phase information reached the recording mikes. I don't know exactly why you're getting those effects on some of that pop material.

In reply to:

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So, I'm thinking for a 99.9% music listener is surround processing really worth the cost for a mainstream music listener.

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Some stereo material works well on PLII and some doesn't. The early Elton John albums Don't Shoot Me, Madman Across the Water, and Honky Chateau are all very flat and don't produce much surround in PLII. Even the remastered stereo versions are the same. By contrast the Goodbye Yellow Brick Road stereo album produces good surround. It's just vastly different.

Dolby has a list of stereo albums that do especially good in PLII: http://www.dolby.com/tech/co.br.0102.PLIIDemo.pdf

The other type of surround is discrete, from multichannel SACD, DVD-A, Digital Dolby or DTS 5.1. This is by far the preferred approach, but material choice is limited.

Even given discrete multichannel, there's no guarantee it will have lots of surround. The other extreme is too much surround, as if a pan pot was rotated continuously during the remix. It's all up to the mixing engineer.

But when it's good, it's really, really good. On a nice Axiom system, good surround is an entirely different dimension. Yet if done properly it's not fake or artificial sounding.

Some examples of superb surround are: Elton John - Goodbye Yellow Brick Road (SACD), Pink Floyd -- Dark Side of the Moon (SACD), David Bowie - Ziggy Stardust (SACD), Eagles - Hotel California (DVD-A), and Fleetwood Mac - Rumours (DVD-A). Don't write off surround until you hear some of these on Axiom speakers, inc'l a subwoofer. Remember you can play the DD 5.1 track of the DVD-As on most any DVD player, so you don't necessarily need a special player.

Intune,

I've never heard Logic7 or DPLII evidence the artifacts that you are hearing. If the recording or track has presence or ambient information, it should always remain consistent throughout that track or over the recording.

I'm almost positive you have an intermittent connection somewhere (it might even be a crack in a circuit board in the processor) that is causing the logic circuits in DPLII or Logic7 to alternately go from full processing to simple stereo (by the way, that's what happens with professional Dolby 5.1 decoders in movie theaters when there is physical damage to the film and the data blocks encoded on the film that contain the Dolby Digital information). The system is designed to default to Dolby Stereo if there is any damage or intermittent data that exceeds the error-correction capacity. I've heard this occasionally in movie theaters, and it's very disconcerting. Check all your interconnects as well.

Regards,

Alan you are right, probably a cracked logic board. I found this out today by connecting my speaker system to a HK avr130. No significant changes in sound output from the left surround with the 130.

I decided to return the 630, and buy a HK avr7200 because I (we) play music more often than watch movies. I will enjoy having the extra headroom the 7200 offers.

One thing I learned (think I am right) is that the total sound output using logic 7 is a lot less than straight stereo. So it can't hurt to have the extra power.


Intune